Ball grinding machine



March 23, 1948. H. A. TOULMIN, JR 2,438,239

BALL GRINDING MACHINE Filed July 23, '1946 4 Sheets-Sheet 1 INVENTOR HARRY A. TOULMIN JR.

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ATTORNEYS March 23, 1948. H. A. TOULMIN, JR 2,438,239

BALL GRINDING MACHINE Filed July 23, 1946 4 Sheets-Sheet 2 use 1 l\\\ l5 W///M/14 MM INVENTOR HARRY A. TOULMIN JR. a

I Joul/mim i J 0 0601401.

ATTORNEYS 1 arch 23, 1948. TQULMIN, JR 2,438,23

BALL GRINDING MACHINE Filed July 23, 1946 4 Sheets-Sheet 3 INVEMTOR HARRY A. TOULNN JR. BIf

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ATTORNEYS Mamh 194$ H. A. TOULMIN, JR 2,438,239

BALL GRINDING MACHINE Filed July 23, 1946 4 Sheets-Sheet 4 HARRY A. TOUL'MN JR. 8 I6 BY ATTORNEYS of a machine particularly Patented Mar 23, 1948 Harry A. Toulmin, Jr., The Thompson Grin Ohio, a corporation Dayton, Ohio, assignor to der Company, of Ohio Springfield,

Application July 23, 1946, Serial N0. 685,714

21 Claims. ll

This invention relates to improvements in grinding machinery and has particular reference to a machine adapted to the grinding of balls or similar contoured articles.

An object of this invention is the provision of a positively controlled ball grinder which shall be substantially continuous in operation and therefore give maximum production.

A further object of the present invention is the provision of an improved mechanism for operation on spherical articles in a continuous stream, which shall cause said articles to be subjected to a maximum of grinding action during the period of their passage through the machine.

A further object of this invention is to provide for a continuous feeding operation on the work pieces or balls in a manner to insure gradual stock removal and permit final proper sizing of the pieces during the continuous progress thereof.

Another object of this invention is the elimination of fixed work supporting members and the utilization of the work pieces themselves as a sole means to produce proper relative movement of work and grinding wheel to effect proper movement and grinding action on the work pieces,

A further object of the invention is the provision of a mechanism for the grinding of balls which will positively and definitely regulate and control the rotating action of the blanks during grinding.

Another object of the invention is the provision of a machine which will automatically operate continuously on a series of spherical articles to successively reduce the work pieces down to the same predetermined size and accurate to fractional thousandths of an inch, both as to diameter, contour, and surface.

Another object of the invention is the provision adapted for the production of spherical articles which will automat ically impart a gyratory or twisting movement to the work pieces to insure proper presentation of its entire surface to the abrasive member.

A further object of this invention is to provide a ball grinding machine with a novel grinding and regulating wheel arrangement serving as the sole means for continuously feeding the work pieces over the grinding wheel to automatically effect a continuous grinding operation on a series of work pieces.

Still another object of this invention is to provide a. novel grinding machine adapted to spherical grinding which is of simple construction and operation, requiring a minimum of special adjustments and setting of the various grinding and regulating wheel spindles.

Further features and advantages of this invention will app ar from a detailed description of the drawings in which:

Figure l is a fragmentary diagrammatic view, partly in section, showing the general arrangement of the ball grinding machine incorporating the features of this invention.

Figure 2 is a fragmentary vertical transverse section on the line 2-2 of Figure 1.

Figure 3 is an enlarged section on the line 33 of Figure 1.

Figure 4 is an enlarged view on the line l-t of Figures 1 and 5 showing the relationship of work and grinding wheel.

Figure 5 is an enlarged fragmentary plan view, indicated by the line 5-5 in Figure 2.

Figure 6 is an enlarged fragmentary section on the line 6-6 in Figure 5.

Figure '7 is an enlarged fragmentary section on the line ll of Figure 5.

Figure 8 shows a modified form of work control mechanism for the machine indicated by the line 8-8 in Figures 9 and 10.

Figure 9 is a fragmentary transverse section on the line 9-4 of Figure 8.

Figure 10 is a, transverse sectional view on the line Ill-10 of Figure 8.

As illustrative of apparatus incorporating the features of this invention, there is shown a machine comprising a base or frame l5, Figure 1, to which is fixed the grinding wheel housing l6 by suitable screws ll. 0n the grinding wheel housing I6 is journaled the grinding wheel spindle i8 on suitable antifraction bearings IS. The grinding wheel G is mounted by suitable taper means 20 on the spindle I 8 and held in place by a nut 2|.

A grinding wheel driving motor 22 is mounted on the grinding wheel housing l6 and has a shaft 23 connected to drive a variable speed unit 24 which in turn has an output shaft 25 supported in a bearing 28 in the housing l6. Adjustment of the control lever 21 of the unit 24 eflects variable speeds in the output shaft 25. A pulley 28 is suitably keyed at 29 to the output shaft 25.

Belts 38, operated over the pulley 28 and the pulley 3|, fixed .by a suitable key 32 to the grinding wheel spindle shaft l8, connect power from the motor 22 to drive the grinding wheel spindle l8 and grinding wheel G.

' Also mounted on suitable guideways 32 on the frame I5 is the regulating wheel housing 33. The guideways 32 are so arranged that the housing 33 moves in a perpendicular direction relative to the axis of rotation 34 of the grinding wheel spindle l8. The regulating wheel housing 33 may be moved on the guideways 32 and accurately positioned relative to the grinding wheel spindle I8 and the grinding wheeel G by manipulating is attached to an adjusting screw 38 journaled against axial movement in a suitable bracket 36 fixed to the base i5 by suitable screws 31. The screw 38 operatively engages in a nut 39 journaled in a block 48 fixed to the housing 33 by suitable screws 4|. The nut 39 is adjustably positioned against rotation by the mechanism best shown in Figure 3 comprising a worm 42 formed on a shaft 43 journaled against aXial movement in suitable bearings 44 and 45 in the block 48, the worm 42 meshing with a worm gear 46 cut on the outside diameter of the nut 39. An indicating dial 41, connected to the shaft 43, serves to indicate the amount of rotation of the shaft 43 and the nut 39 for the final accurate vernier positioning of the regulating wheel housing 33. R- tation of the hand wheel 35 effects the coarse positioning and rapid movement of the housing 33 to and from the grinding wheel G. A clamping screw 48 operated by a hand wheel 49 serves to clamp the main screw 38 in its position while allowing the final fine adjustment to be effected by rotating the knob 58 and vernier dial 41 on the shaft 43.

On the regulating wheel housing 33 is journaled the regulating wheel spindle on suitable bearings 52, this spindle having appropriately mounted on its taper portion 53 the regulating wheel R which is held in place by the nut 54. The regulating wheel spindle 5| is driven from the regulating wheel drive motor 55 which is mounted on the regulating wheel housing 33 and has a shaft 56 connected to drive the variable speed unit 51 which in turn has the output shaft 58 supported at its outer end in a suitable bearing 59 in the regulating wheel housing 33. Manipulation of the control lever 68 of the variable speed power unit 51 effects variable output speeds in the shaft, 58. A pulley 6| fixed by a suitable key 62 to the output shaft 58 is connected by belts 63 to a pulley 64 fixed by the key 65 to the regulating wheel spindle 5|.

The grinding wheel G is dressed so that it has a frusto-com'cal portion 66 and a straight cylindrical portion 61. The regulating wheel is similarly dressed with a frusto-conical portion 68 and a straight cylindrical portion 69. The grinding wheel G and the regulating wheel R are placed on the respective spindles l8 and 5|, Figure 1, with the large diameters or base portions of the frustoconical portions 66 and 68 in alignment and with the smaller diameter portions at the other end of the frusto-conical portions in alignment. With this arrangement, a variable width grinding throat T is formed between the wheels increasing in width from left to right as shown in Figures 1 and 5. The straight cylindrical portions 61 and Marc also arranged adjacent one another and at the widest part of the throat T.

the hand wheel 35, Figure 1, which In the conical portion 68 of the regulating wheel R is formed a spiral or helical feed groove 18 which is preferably made with a radius of curvature equal to the work pieces or balls W to be ground.

Both the grinding wheel G and the regulating wheel R are maintained in proper condition by crush dressing apparatus. The grinding wheel G is dressed by a crush dressing device comprising a guide bar 1| pivotally mounted about a trunnion 12 fixed to the grinding wheel housing l6. On the outer ends of the guide bar 1| are formed elongated slots 13 through which pass clamping screws 14 into the housing l6, the screws 14 when tightened serving to lock the guide bar 1| inany desired angular or straight position relative to the grinding spindle axis 34 to conform to the desired angles or cylindrical straight portion desired on the grinding wheel G. Slidably mounted on suitable guideways on the guide bar H is the carriage 15 which is appropriately moved along the guide bar by screw 16' rotated by a hand wheel 11. Rotation of the hand wheel 11 traverses the carriage longitudinally of the grinding wheel G. On the carriage 15 is a cross slide 16 upon which is journaled the crush dressing wheel 11, the cross slide being actuated by a screw 18 upon rotation of the hand wheel 19. Thus, by properly setting the guide bar 1| and adjusting the cross slide and then feeding the carriage 15 longitudina ly of the grinding wheel by the hand wheel 11, a crush dressing operation may be performed on the grinding wheel to properly condition it for carrying out the required grinding operation.

Similarly the regulating wheel R is dressed by a crush dressing apparatus comprising the guide bar 88 mounted on the pivot screw 8| on the regulating wheel housing 33 and locked in any desired angular position byv means of the clamp screws 84 in the elongated slots 85 in the ends of the guide bar 88. A carriage 88 is mounted on antifriction guideways 81, Figure 2, for substantially friction-free sliding movement along the guide bar 88. A cross slide 88 is mounted on the carriage 86 and contains the crush dressing wheel 89 suitably journaled thereon. A cross feed screw 98 serves to adjust the cross slide on the carriage 86 by manipulation of the hand wheel 9|.

With the guide bar 88 set in the correct angular position and the crush dressing ,wheel 89 moved in to the previously formed helical groove 18 of the regulating wheel, the lead of the helical groove will automatically feed the carriage 86 along the guide bar 88 to effect the proper crush dressing of the helical groove 18. The bar 88 may be adjusted to a straight position parallel to the axis of rotation 92 of the regulating wheel spindle when it is desired to crush dress the straight portion 69 of the regulating wheel R.

The operation of the machine is as follows: The grinding wheel drive motor 22 and the regulating wheel drive motor 55 are energized and their respective variable speedunits 24 and 51 a suitable or balls W are then continuously fed to the throat T formed between the grinding and regulating wheels. The balls are started into this throat at the larger diameter end portions S of the grinding and regulating wheels, that is, the narrower portion of the variable width throat T. Preferably, a suitable hopper (not shown) connected through a feed tube 92a serves to continuously supply the work or balls W to the throat T begimiing at the edges SI of the grinding and regulating wheels.

With the regulating and grinding wheels rotating in the same direction, counterclockwise in Figures 2 and 10, and with the spiral feed groove H3 so arranged (as a left-hand thread) as shown in Figures 1 and 5, it will be noted that the balls will automatically be guided in feeding and grinding motion longitudinally of the grinding and regulating wheels. As seen in Figures 4 and 8, the path of travel 93 of the balls through the throat is angularly related to the plane P defined by the axes of rotation 34 of the grinding wheel and the axis of rotation 92 of the regulating wheel. In other words, the balls start in at the point s and gradually move down a path 93 angularly related by the angle A, Figures 4 and 8, to the common plane P defined by the axes of the grinding and regulating wheels.

As the balls W emerge from the throat between the frusto-conical portions of the grinding and regulating wheels at the point E, they then pass through the straight cylindrical portions 61 and 69 supported on a guide blade 94 carried on a support Ma fixed to the housing i6 for final sizing and polishing of the balls. The halls then proceed outwardly into the discharge trough 95 and through an opening 96 in the base I5 where they drop into a suitable container in finished condition.

It is to be clearly. noted that not only do the balls proceed downwardly along the line 93 in angular relationship to the axes of rotation 34 and 92 of the grinding and regulating wheels but there is no other guiding support for the balls during this operation since the angular frustoconical portions, together with the spiral feed groove formed on the regulating wheel R, provides the sole means for controlling the feeding grinding and in continuously rotating the balls to eifect a thorough and accurate uniform grinding of the work over their entire spherical surface. Thus, a continuous process of feeding the Work pieces through the feed tube 9201 into the throat at the point S and the automatic movement of the balls through the widening throat along the line 93 to the point E and then the final sizing and polishing up operation by the straight portions 61 and 69 of the grinding and regulating wheels provides a continuous uniform and efficient process for finishing spherical pieces.

As a modification, there is shown in Figures 8, 9, and an arrangement to hold down and steady the balls in proper operative contact with the grinding and regulating wheels. This apparatus consists of a bracket 91 rigidly fixed to the housing It by suitable screws 98 and which carries a pivot pin 99 upon which is pivotally mounted the bar Hit. A pin llll, fixed to the bracket 9'! and operating in the elongated slot I02, serves to limit the pivotal motion of the bar Hill. A work contacting strip I03, carried on guide screws I04 and guide strips I05 and yieldingly urged normally downwardly by springs I06, has a surface Nita adapted to lightly contact the work or balls W and maintain a predetermined pressure between the work and the grinding and regulating wheels for more efficient operation of the machine at a high speed.

While the apparatus herein disclosed and described constitutes a preferred form of the invention, it is to be understood that the apparatus is capable of mechanical alteration without departing from the spirit of the invention and that such mechanical arrangements and commercial adaptations as fall within the scope of the appendant claims are intended to be included herein.

pieces comprising the steps of: rotating a pair of frusto-conicalabrasive wheels on parallel axes to form a variable width grinding throat; driv-- ing one of said wheels more rapidly than the other and both in the same direction; and continuously feeding a series of spherical work pieces through said throat from the narrower width to the wider width thereof.

3. The method of grinding spherical work pieces in a continuous manner comprising the steps of rotating a grinding and a regulating wheel on parallel axes lying in a horizontal plane, said wheels being shaped to provide a tapered grinding throat therebetween, rotating said wheels in the same direction and one more rapidly than the other, and feeding a series of spherical work pieces into the narrower end of said throat while. causing said spherical work pieces to move at a downwardly inclined path of travel toward the wider end of said throat to perform a grinding operation on said Work pieces.

4. The method of grinding spherical work pieces comprising rotating a frusto-conically shaped grinding wheel on a horizontal axis at grinding speed, rotating a frusto-conically shaped regulating wheel on a horizontal axis parallel to said grinding Wheel axis, grinding and regulating wheels another to form a grinding throat of increasing width extending longitudinally of said axes, and continuously feeding a series of spherical work pieces into the narrower end of end of said throat and causing said work piece to move through said throat from a position above a plane defined by said axes in inclined downward movement into said plane at the compleportions formed on tion of the grinding operation, and effecting longitudinal movement of said work piece by said regulating wheel in a direction substantially arallel to said axis of rotation of said grinding and regulating wheels.

6. In a ball grinding machine, a conically shaped grinding wheel and conically shaped regulating wheel located adjacent one another to form a variable width throat therebetween, means for rotating said grinding wheel at grinding speeds, means for rotating said regulating wheel at feeding speeds, and means formed on said regulating wheel to move a spherical work piece when placed in the narrower end of said throat toward the wider portion of said throat.

7. In a grinding machine for spherical work pieces, a grinding wheel having a frusto-conical portion and a straight cylindrical portion mounted on a power driven grinding wheel spindle, a regulating wheel having a frusto-conical portion formed with a helical groove therein and a straight cylindrical portion, means for mounting said regulating wheel on a power driven spindle so that said conical and cylindrical portions are aligned with like portions of said grinding wheel, means for feeding a series of spherical work pieces into the throat formed between said abrasive wheels, and means for rotating said grinding and regulating wheels at predetermined relative speeds to effect a through feeding movement of said work pieces in a diagonally downward direction between said abrasive wheels and to feed said work pieces in a horizontal direction past said cylindrical portions of said wheels to complete a grinding operation on said work pieces.

8. In a ball grinding machine, a frame, a grinding wheel spindle journaled for rotation about a horizontal axis on said frame, a regulating wheel spindle journaled on said frame for rotation about a horizontal axis lying in the same plane as said first mentioned axis, a conical grinding wheel on said first mentioned spindle, a conical regulating wheel on said second mentioned spindle, means for relatively said spindles so as to form a variable width grinding throat between said wheels, and means for feeding a series of spherical work pieces into the small end of said throat so as to cause said work pieces to move in downwardly inclined direction from a position above said mentioned plane to a position lying in said plane to complete a grinding operation on said work pieces.

9. In a ball grinding machine, a frame, a grinding wheel spindle journaled for rotation about a horizontal axis on said frame, a regulating wheel spindle journaled on said frame for rotation about a horizontal axis lying in the same plane as said first mentioned axis, a conical grinding wheel on said first mentioned spindle, a conical regulating wheel on said second mentioned spindle, means for relatively positioning said spindles so as to form a variable width grinding throat between said wheels, and means for feeding a series of spherical work pieces into the small end of said throat so as to cause said work pieces to move in downwardly" inclined direction from a position above said mentioned plane to a position lying in said plane to complete a grinding operation on said work pieces, cylindrical said grinding and regulating wheels at the wide end of said throat, and guide means for receiving and supporting said work pieces while moved parallel to said axes out positioning straight portions of said grinding throat by the preceding work pieces passing through said variable throat.

10. In a ball "grinding machine, a grinding wheel and a regulating wheel rotatable on parallel horizontal axes lying in a common horizontal plane, both of said wheels comprising frusto-conical portions and straight cylindrical portions adjacent the conical portions said wheels being adjacent with their cylindrical portion extending in the same direction so as to provide a variable width grinding throat between said wheels, means for continuously feeding a series of spherical work pieces to the narrowest end of said throat, means for rotating said wheels at predetermined relative rates and directions of rotation to cause said work pieces to feed longitudinally of the axes of rotation of said wheels in a downwardly inclined direction from a position above said plane into said plane upon arrival of said work pieces at said cylindrical portions of said wheels, and means including a supporting-blade for guiding said work pieces, as pushed by the preceding work pieces coming from said conical portions of said wheels, out past the end of said cylindrical portions to complete the grinding operation on said work pieces.

11. In a ball grinding machine, a grinding wheel and a regulating wheel rotatable on parallel horizontal axes lying in a common horizontal plane, said wheels comprising frusto-conical portions and straight cylindrical portions adjacent the conical portions on both of said wheels, said wheels having their respective conical and adjacent so as to provide a variable and straight grinding throat between said wheels, means for continuously feeding a series of spherical work pieces to the narrowest end of said throat, means for rotating said wheels at predetermined relative rates and directions of rotation to cause said work pieces to feed longitudinally of their axes of rotation of said wheels in a downwardly inclined direction from a position above said plane into said plane upon arrival of said work pieces at said cylindrical portion of said wheels, means including a supporting blade for guiding said work pieces as pushed by the preceding work pieces coming from said conical portions of said wheels out past the end of said cylindrical portions to complete the grinding operation on said work pieces, and means on said regulating wheel comprising a helical groove formed on the conical portion thereof to facilitate the feeding movement of said work pieces between said grinding and regulating wheels.

12. In a ball grinding machine having a grinding wheel and a regulating wheel, each of said wheels having complementary conical and straight cylindrical portions and said regulating wheel having a spiral groove thereon, means for rotating both of said wheels so that work pieces may be fed through the throat formed between said wheels by the said groove, said wheels forming the sole means for guiding, feeding, and sizing the work pieces as they pass through said throat toward said cylindrical portions.

13. In a ball grinding machine having a grinding wheel and a regulating wheel, each of said wheels having complementary conical and straight cylindrical portions and said regulating wheel having a spiral groove thereon, means for rotating both of said wheels so that work pieces may be fed between the throat formed between said wheels by said groove whereby said wheels form the sole means for guiding, feeding, and sizing the work pieces as they pass through said throat toward said cylindricalportions, and guide bar means associated with said cylindrical portions to assist in guiding said work pieces when being operated upon by said cylindrical portions of said wheels.

14. In a ball grinding machine having a conical grinding wheel, a conical regulating wheel including a helical feed groove formed thereon, means for rotatin said wheels in predetermined grinding and feeding relationship, and means for continuously supplying a series of spherical work pieces into the grinding throat formed between said wheels, whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said grinding and regulating wheels.

15. In a ball grinding machine having a conical grinding wheel, a conical regulating wheel including a helical feed grooveformed thereon,

' means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical work pieces into the grinding throat formed between said wheels, whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said grinding and regulating wheels, and straight cylindrical pertions formed on said wheels and a guide bar located between cylindrical portions of said wheels adapted to receive said work pieces coming from said conical portions to said cylindrical portions to eilect the guiding of said work pieces as moved parallel to said axes out of said cylindrical portions of said wheels by the oncoming work pieces being ground on said conical portions of said wheels.

16. In a ball grin-ding machine, a conical grinding wheel, a conical regulating wheel, a helical feed groove formed on said regulating wheel, means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical work pieces into thegrinding throat formed between said wheels whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said wheels, and a holddown bar positioned to bear downwardly on said work pieces during their passage between said wheels. I

17. In a ball grinding machine, a conical grinding wheel, a conical regulating wheel, a helical feed groove formed on said regulating wheel, means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical work pieces into the grinding throat formed between said wheels whereby said work pieces feed through said throat in a diagonal direction rela tive to the aXes of rotation of said wheels, and a hold-down bar positioned to bear downwardly on said Work pieces during their passage between said wheels, said bar being pivotally supported intermediate its ends for alignment with the line of work pieces between said wheels.

18. In a ball grinding machine, a conical grinding wheel, a conical regulating wheel, a helical feed groove formed on said regulating wheel, means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying the series of spherical work pieces into the grinding throat formed between said wheels whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said wheels, and a holddown bar positioned to bear downwardly on said work pieces during their passage between said wheels, said bar being pivotally supported for alignment with the line of work pieces between said wheels and including a yieldable pressure plate bearing directly on the said work pieces.

19. In a. ball grinding machine having a conical grinding wheel, a conical regulatingwheel including a helical feed groove formed thereon, means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical work pieces into the grinding throat formed between said wheels, whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said ndi g and regulating wheels, and straight cylindrical portions formed on said wheels, a guide bar located between cylindrical portions of said wheels adapted to receive said work pieces coming from said conicalfportions to said cylindrical portions effect the guiding of said work pieces as moved parallel to said axes out of said cylindrical por-' tions of said wheels by the oncoming work pieces being ground on said conical portions of said wheels, and a pressure bar bearing on the line of work pieces between the conical parts of said wheels to urge the said work pieces into working engagement with said wheels.

20. In a 'ball grinding machine having a conical grinding wheel, a conical regulating wheel including a helical feed groove formed thereon,

means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical workpieces into the grinding throat formed between said wheels, whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said grinding and regulating wheels, and straight cylindrical portions formed on said wheels, a guide bar located between cylindrical portions of said wheels adapted to receive said work pieces coming from said conical. portions to said cylindrical portions to effect the guiding of said work pieces as moved parallel to said axes out of said cylindrical portions of said wheels by the oncoming work pieces being ground on said conical portions of said wheels, and a pressure bar bearing downwardly on the work pieces between the conical parts of said wheels and pivoted intermediate its ends for alignment with the line of said work pieces for urging the same into working engagement with said wheels.

21, In a ball grinding machine having a conical grinding wheel, a conical regulating wheel including a helical feed groove formed thereon,

means for rotating said wheels in predetermined grinding and feeding relationship, means for continuously supplying a series of spherical work pieces into the grinding throat formed between said wheels, whereby said work pieces feed through said throat in a diagonal direction relative to the axes of rotation of said grinding and regulating wheels, and straight cylindrical portions formed on said wheels, a guide bar located between cylindrical portions of said wheels adapted to receive said work pieces coming from said conical portions to said cylindrical portions to efi'ect the guiding of said work pieces as moved parallel to said axes out of said cylindrical portions of said wheels by the oncoming work pieces being ground on said conical portions of said wheels, and a pressure bar positioned over the throat between said wheels for bearing downwardly on the work pieces therein, said bar being emes pivotally supported intermediate its ends for Number Name Date alignment with the work pieces and includin 1,579,934 Helm Apr. 6, 1926 a yleldable pressure plate bearing d ectly on the 1,683,974 Heim Sept, 11, 1928 saidwork pieces. 1,846,661 Vuilleumier Feb. 23, 1932 HARRY A. T TE- J 5 1,872,405 Caster Aug. 16, 1932 1,970,777 Smith Aug. 21, 1934 REFERENEES CITED 2,062,803 Benedek Dec, 1, 1936 The following references are of record in the 2,037,374 88 y 20, 1937 mm 10 2122 222 e e? 1:22

' Inns e a. une

UNITED STATES PAWS 2,377,982 Theler et a1 June'12, 1945 Number Name Date 80 Mason Jan. 7, 1947 611,968 Kempster 0st. 1893 

